The present invention relates to a fuel injection controller for use in an engine, having a direct injector for injecting fuel into a cylinder and an intake injector for injecting fuel into an intake passage, to control the drive mode of the injectors based on the operation condition of the engine.
Such an engine is supplied with fuel in one of the next injection modes.
(a) Fuel is supplied to the engine by only the direct injector (in-cylinder injector).
(b) Fuel is supplied to the engine by only the intake injector.
(c) Fuel is supplied to the engine by both the direct injector and the intake injector.
The supply of fuel to the engine by both the direct injector and the intake injector when the engine is idling reduces the amount of fuel that is injected by the intake injector and deposited on the walls of the intake passage. This enables the target speed (the target engine speed during idling) to be lowered so that the fuel efficiency can be improved.
However, when the target speed is set to a lower value, the engine is prone to stall. Therefore, measures should be taken to avoid such a problem.
Japanese Laid-Open Patent Publication No. 2002-364409 describes an example of a fuel injection controller for an engine in the prior art. The controller described in the publication drives a direct injector in addition to an intake injector when performing homogeneous combustion. In this controller, however, the engine may stall if the target speed is reduced. Therefore, it is difficult to lower the target speed with this controller.